Torque responsive release clutch for a power nutrunner

Abstract

A torque responsive release clutch intended for a power nutrunner and comprises a driving clutch half ( 11 ) and a driven clutch half ( 10 ) coupled to each other for torque transfer by means of axially directed teeth ( 16, 17 ), wherein one of the clutch halves is axially movable between an engagement position and a release position against the action of a bias spring ( 13 ). Each one of the teeth ( 16 ) of one of the clutch halves ( 10 ) has a substantially prismatic shape and extends axially from a base portion ( 19 ) to a top portion ( 20 ) and comprises two surfaces ( 22, 23 ) which form between them a ridge ( 25 ). The base portion ( 19 ) of the tooth ( 16 ) has a radial extent from an inner diameter (d 1 to an outer diameter (d 2 ), and the ridge ( 25 ) extends from the inner diameter (d 1 at the base portion ( 19 ) to the outer diameter (d 2 ) at the top portion ( 20 ). The contact points between teeth ( 17 ) of the driving clutch half ( 11 ) and the teeth ( 16 ) of the driven clutch half ( 10 ) are arranged to travel along the ridge ( 25 ) during the release sequence of the clutch, whereby the torque coupling of the clutch is transferred via a smaller diameter at the beginning of the release sequence than at the end thereof. This means that the dynamic torque additive emanating from the inertia of the movable clutch half at the beginning of the release movement is added to a torque level that is lower than that at the end of the release sequence.

1. A torque responsive release clutch for a power nutrunner, comprising:
 a first clutch half and a second clutch half, both provided with axially extending teeth for torque transfer between the clutch halves, 
 wherein:
 either one of said first and second clutch halves is axially movable between an engagement position and a release position, 
 a spring unit is arranged to bias the movable clutch half towards the engagement position, 
 each one of the teeth on said first clutch half has a substantially prismatic shape and extends from a base portion to a top portion, said base portion having a radial extent between an inner diameter and an outer diameter, 
 each one of the teeth on said first clutch half comprises a ridge extending from said base portion at said inner diameter to said top portion at said outer diameter, and 
 each one of the teeth of said second clutch half is arranged to engage a corresponding tooth of said first clutch half at an engagement point that travels along said ridge of said corresponding tooth of said first clutch half when the movable clutch half is displaced from the engagement position to the release position, whereby the engagement point between each tooth of said first clutch half and each tooth of said second clutch half is displaced from said inner diameter to said outer diameter during a clutch release sequence. 
 
 
     
     
       2. The torque responsive release clutch according to  claim 1 , wherein said prismatic shape includes a first surface extending substantially in a plane tangential to a clutch rotation direction and leaning outwards from said inner diameter at said base portion to said outer diameter at said top portion, and a second surface extending in a plane substantially radial to the clutch rotation direction from said base portion to said top portion and leaning forwards in the clutch rotation direction wherein said first and second surfaces form said ridge between them. 
     
     
       3. The torque responsive release clutch according to  claim 2 , wherein said second surface extends in a plane differing from the radial direction of the clutch by at least two degrees.